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    <title>第一周小作业</title>
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    <table>
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            <tr>
                <th colspan="2"></th>
                <th>Name</th>
                <th>Mass(10²kg)</th>
                <th>Diameter(km)</th>
                <th>Density(kg/m³)</th>
                <th>Gravity(m/s²)</th>
                <th>Length of day(hours)</th>
                <th>Distancd from Sun<br>(10⁶km)</th>
                <th>Mean temperature(°C)</th>
                <th>Number of moons</th>
                <th>Notes</th>
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        <tbody>
            <tr>
                <th rowspan="4" colspan="2" class="big">Terrestrial planets</th>
                <th class="big">Mercury</th>
                <td>0.330</td>
                <td>4,879</td>
                <td>5427</td>
                <td>3.7</td>
                <td>4222.6</td>
                <td>57.9</td>
                <td>167</td>
                <td>0</td>
                <td>Closest to the Sun</td>
            </tr>
            <tr>
                <th class="big">Venus</th>
                <td>4.87</td>
                <td>12,104</td>
                <td>5243</td>
                <td>8.9</td>
                <td>2802.0</td>
                <td>108.2</td>
                <td>464</td>
                <td>0</td>
                <td></td>
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                <th class="big">Earth</th>
                <td>5.97</td>
                <td>12,756</td>
                <td>5514</td>
                <td>9.8</td>
                <td>24.0</td>
                <td>149.6</td>
                <td>15</td>
                <td>1</td>
                <td>Our world</td>
            </tr>
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                <th class="big">Mars</th>
                <td>0.642</td>
                <td>6,792</td>
                <td>3933</td>
                <td>3.7</td>
                <td>24.7</td>
                <td>227.9</td>
                <td>-65</td>
                <td>2</td>
                <td>Thr red planet</td>
            </tr>
            <tr>
                <th rowspan="4" class="big">Jovian planets</th>
                <th rowspan="2" class="big">Gas giants</th>
                <th>Jupiter</th>
                <td>1898</td>
                <td>142,984</td>
                <td>1326</td>
                <td>23.1</td>
                <td>9.9</td>
                <td>778.6</td>
                <td>-110</td>
                <td>67</td>
                <td>The largest planet</td>
            </tr>
            <tr>
                <th class="big">Saturn</th>
                <td>568</td>
                <td>120,536</td>
                <td>687</td>
                <td>9.0</td>
                <td>10.7</td>
                <td>1433.5</td>
                <td>-140</td>
                <td>62</td>
                <td></td>
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                <th rowspan="2" class="big">Ice giants</th>
                <th>Uranus</th>
                <td>86.8</td>
                <td>51,118</td>
                <td>1271</td>
                <td>8.7</td>
                <td>17.2</td>
                <td>2872.5</td>
                <td>-195</td>
                <td>27</td>
                <td></td>
            </tr>
            <tr>
                <th class="big">Neptune</th>
                <td>102</td>
                <td>49,528</td>
                <td>1638</td>
                <td>11.0</td>
                <td>16.1</td>
                <td>4495.1</td>
                <td>-200</td>
                <td>14</td>
                <td></td>
            </tr>
            <tr>
                <th colspan="2" class="big">Dwarf planets</th>
                <th id="high">Pluto</th>
                <td>0.0146</td>
                <td>2,370</td>
                <td>2095</td>
                <td>0.7</td>
                <td>153.3</td>
                <td>5906.4</td>
                <td>-225</td>
                <td>5</td>
                <td>Declassified as a planet in 2006,but this <a href="#" id="purple">remains controversial</a>.</td>
            </tr>
        </tbody>
    </table>
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